Electrical indicating device



E. B. MOSS ET AL ELECTRICAL INDICATING DEVICE Oct. 14, 1952 4 Sheets-Sheet 1 Filed Dec. 7, 194a IEW WH Q v 3) m if Maw Oct. 14, 1952 E. B. MOSS ETAL 2,614,244

ELECTRICAL INDICATING DEVICE Filed Dec. '7, 1948 4 Sheets-Sheet 2 4g x g 10 626 29 32 530 27 161% f9 3% INVENTORs E R/C BEECRO I 0 CHARLES WILL/AM 0001 62 5) mm go,

Oct. 14, 1952 E. B. Moss ET AL ELECTRICAL INDICATING DEVICE 4 Sheets-Sheet 4 Filed Dec. 7, 1948 TRANSMITTER.

55/6 fifECEOFT M055 CH/IKLES MAL/HM 6001 56 thereon a fixed distance, apart. movementof ;the..,armatures; relative to the;coi-ls rand. the. coils associated with-the vtwoarmatures are spaced ,apart ;in-;said direction- :of;-.move ment Patented Oct. 14, 1952 UNITED STATES PATENT Price :ELECTRICAL; INDICATING DEVICE IErid'BeecrOftjMoss and Charles William Cooper, Cricklewood, London, England .aApplicationzDecember 7, 1948,-Serial No. 6 3,874 In GreahBritain October 31, 1947 .This invention relates to electrical. indicating .devicesand has a particular. application in. .de-

vices. for providing an indication ,at a remote ,pointof. the: displacement of an element.

=One object .of this invention isto provide. an

indicating .device energised by an alternating current poweresupply,

the indication oi which, is notaltered by.:changes.in.the voltage and/orlthe frequency of.v the power supply.

.,-According to this invention, anelectricalindicating device .-comprisesea pair of impedances uenergisedv .in.,par.a1lel by .an alternating. current ,power. supply. meansior; varying the. magnitude yet one or.-both impedances sothat the ratio. of their .ximpedance .var-ies .ing-accordance .with ,a. I quantityto be indicated and means for indicatin the ratio of the currents through the two imped- The. aforesaid means for-varying the magnitude of th .impedances may-be so. arranged. thatrone impedance. increases aswthe. other decreases.

PreferabIy each-oi .said. impedancescomprises a variable inductor.-:and-. in this arrangement, one ..or each of the inductors.maytcomprise .a ,-coi1-.or coils. associated with a: ferro-magnetic armature, :means being, provided iorvarying the position ,of .the 1 armature in relation, to said coil: or :coils in accordance with the.; quantity- .-to. be indicatedso as .to vary \the .impedanceiof the inductor inthe required manner.

,The indicating :means maycomprise 1a rationieter ofaanyiapp q te typ .In the arrangement. in. which anqarmature. is

.-':associated with-each inductor; the twoarmatures may be carried on: apsingle .mountingand spaced in the -direction of by, a distance difierentzfrom the spacing .of;. the armature. i For .example, 1 the armature may; be

I slightly furthenapart than the. coils; so that'when themid-point of I the armature amountin coincides .with .the;:;mid -point; ofg the: coilzsmounting, then. ,a movement in one direction will make one armature move. close/to its associated coiiwhilst the other armature moves away,from..its -associxEach armature may, be, so: shapedthat; by rela- '.tive rotation of the armaturewandits associated -.coil or.-,coi1s about .an1axisin :said direction of movement, the inductance of the eoilzorncoilsds .varied. .If theaxial spacingibetweenthergarmaturesvdiffers .from' the; axial;spacing;.between Zthe coils; then in, general; the two. armaturesaregnot 'mainbody part. 12 of a housing. Theifre'e end ofthe bellows is secured toone end otan alumi- 11111111 alloyrod l3- which forms anarmature mounting. .To the other end of :the-rod= is* fiiced :a .cup I tadapted to. receive-oneendh-f a helical a pressure indicating similarly situated with regard to their respective coils and the efiect of thearmature rotationwill ,diner for the two inductors. ;'Thus,',the;relative rotation of the armatures andtheir associated coils causes the ratio of the impedances of the two inductors .to vary andthereiore1enables:the

calibration to be, adjusted.

Preferably in an indicating "deviceaccording to the present invention the impedancesihave low loads at thefreq ency o th a tern tinecu ren power suppl r bythe ind cat o r v dedl substantiallyindependentof slight variations in supply frequency, .such .as are inevitable in practice.

,The indicating. deviceaccording to this, invention is particularly suitablejlfor providing A an indication of. apressure ,ata remote point. 1 Thus according to: a, further feature of the,inventio ri an electrical indicating device, of the kindjherein before described. andin whichat least one of the inductors comprises .acoilor coils With amovable armature, is proyided with a pressure lbellowsfarranged toalter the positionof the movable amiature relative to ,the coil .or .,coils in, accordance withapressureto be indicated byisaid indiqaliiQ means.

The following .is a description of ,one emhbiiiment of the invention, refer'encembeing. mad fgto the accompanyingdrawings,inwhich,. 1

Figure 1 is an end .view of;a. transmitter;off. a deyicewith thacoyerflj plate partlycut away;

Figure. 2. is a. transverse section. along the line .2-.-2 ofFigure 1;

.FigureBis a plan view lwiththe, plug assembly removed and partly in. section alonatheiyl ine lii of Figure l; I

Figure 4 is part of.asectionalongthe1ine ,4-4

of Figure 3;.and 'y Fi e 5 is a rcui i eram. o h indicatin device. f I

As is best seen in"Figure'2,the;transmitter of the remote pressure-indicating device is provided with a pressure bellows l 0;0116' end of whichis secured to anend plate II which is-boltedto=the spring I 5 which applies. a resist-ingLforcev tohthe rod l3 and hence to the bellows I0 alonghthe 1 axis of the housing. iThepressuretoube measured I is applied vthrough; ,apasuitable connecting: v -1iozzle I] 6 mthe; end plate .1 I; to the insideof the bellows the holes 3|, of the core to other hole 3|.

l so that the armature mounting l3 will be displaced along the axis of the housing by an amount according t the pressure applied.

The housing I 2 is made of a non-magnetic material such as aluminium alloy and towards the end remote from the bellows is provided with an internal sleeve H which is of cylindrical form about the axis of the rod I3 and th spring and which is provided with an internal screw thread [8. The end of the helical spring remote from the armature bears against an internal shoulder 59 in the bore of a cylindrical element which is provided with an external screw thread adapted to engage the internal thread l8 of the sleeve. Thus, as will be described later, by rotation of this element the initial pressure of the helical spring may be adjusted.

The armature mounting carries two armatures 20, 2| spaced apart one at each end of the bush ,22 carried on the rod [3 and each formed of laminated ferro-magnetic material, the laminations lying in a plane'transverse to the axis of the housing. As is seen in Figure 4, in section in this transverse'plane each armature is circular but has two segments 23, 24 sides of the axis. Thus in one diametral direction the armature has a greater diameter than in the'transverse direction.

' The two armatures are arranged on the mountingwith their corresponding respective diametral axes of symmetry at right angles to one another. Associated with each armature is a pair of coils 25, 26 and 21, 28 wound on laminated annular cores 29, 30 encircling the armatures. Each core has its axis substantially on the armature axis and an internal diameter slightly greater than the larger diameter of the armature. Each core has two pairs of axial holes as indicated by the references 3| on Figure 4 which holes are symmetrically situated on opposite sides of a diameter, the axis of the two holes of a pair subtending an angle of 120 at the axis of the core. Each hole is connected by a radially extending slot 32 to the inner side of the core to facilitate winding of the coils as each coil is wound so that its turns pass through both the holes of a pair. Each turn of a coil thus passes along a sector on one face of the core, through one of thence back along the opposite face The two coils on diametrically opposite sides of the core are connected in series so as to form a single inductor. It will be seen that the inductance of this inductor will vary with the axial displacement of the armature and will also vary as the armature is rotated being greater when the larger diameter of the armature lies in this path.

The coils associated with each armature are similar and the two cores are carried on a spacer 32 which is arranged so that the distance apart axially of the cores 29 and 3E) and their coils isless than the axial spacing of the armatures Thus axial movement of the armature mounting l3 will move one armature closer to its associated coils as the other armature moves away from its coils. The spacer 32 is arranged so that the two coils on one core are situated similarly on opposite sides of a diameter at right angles to the corresponding diameter of the other pair of coils so as to reduce coupling to a minimum.

The spacer 32, which with its associated coils forms a stator, is provided with a cylindrical outer surface adapted to fit in a cylindrical part cut away on opposite of the sleeve I! in the housing l2, and is secured by pins 33.

A tapped hole is provided through the spacer 32 and the sleeve I! to accommodate a lead ferrule 34 through which the leads 35 from the coils are taken to a connecting plug 36 which is mounted on the housing.

Since the axial spacing between the armatures 20, 2| differs from the axial spacing of the inductor coils, the effect on the inductances of the two inductors of rotation of the armature differs and use is made of this feature to compensate for variations in calibration between difierent instruments as will be described hereinafter. In this instrument the adjustment is made by rotating the stator assembly including the spacer 32 and sleeve IT. This adjustment has to be effected without rotation of the armature and without altering the tension of the spring [5.

As previously explained, the spring tension is adjusted by rotating the threaded cylindrical element 28 in the sleeve ll. This rotation is effected by means of the four axially extending holes 37 (Figures 1 and 2) in the outer end of the element 23 and, after adjustment, the element 20 is locked to the sleeve H by means of a locking tab 38 which is secured by a nut 39. This nut is carried on a grub-screw 40 which extends into the bore of a bush 4! in which slides an enlarged bearing portion 42 at the end of the armature carrying rod I 3. The grub-screw 40 thus also serves to limit the travel of the armature if an excessive pressure is applied to the bellows. The bush 4| is provided with an outwardly extending flange 43 which abuts against a shoulder on the sleeve l1 and is drawn towards the shoulder when the nut 49 is tightened.

Two holes 44 (Figure 1) are provided for rotating the stator within the housing. These two holes are extended inwardly with tapped portions to receive the bolts 45 which secure the end cover plate 43 of the housing. For locking the stator after adjustment, there are provided four nuts 4! carried on bolts 48. The heads of these bolts are secured in a first clamping ring 49 which abuts the end of the cylindrical element 20. Tightening of the nuts 4'! draws this clamping ring 49 towards a second clamping ring 50 which abuts against an inwardly extending shoulder 5| on the outer housing l2. The outer surface of the sleeve I7 is also provided with a shoulder 52 which engages a corresponding abutment on the inner surface of the housing so that, when the nuts 4! are tightened, the sleeve I! is locked to the housing [2.

The assembly thus far described forms a transmitter having two inductors, the ratio of the inductances of which is altered in accordance with movement of the bellows which causes axial displacement of the armature. To compensate for variations in manufacture, such as, for example, variations in the strengths of the helical springs between different transmitters, the stator may be rotated to vary the relative inductances so adjusting the calibration of the transmitter. By means of such adjustments interchangeability of transmitters can be ensured.

The receiver, which may be located remotely from the transmitter, employs any convenient type of ratiometer such as for instance that described in the specification of U. S. Patent No. 2,457,685.

Referring to Figure 5, the transmitter is indicated diagrammatically by the rectangle 60 containing the two variable inductors GI, 62.

f lliei'eelver indicated by ftlie'mctangla 63 lneludes"'a rationieter which hastwo -coils 64. 565. -A pre' set resistance "66 is "connected in shunt across one of the coils oftheratiometer'in' order *to" compensate" for any production differencesin I The indicating system is energised'irom an alternating current'po'wer supply 61 which is applled to two "parallel paths each comprising in series one of the inductors 6 I 62 an" adjustable inductance 68, a half -Wave rectifier "69 and one "ofthe ratiometer 'coils"64,65. Inshunt across each rectifier 6 9 and 'iatio meter can is connected a second half Wave rectifier" 10 "having opposite polarityfto the rectifier-69sdthat'the currents "through the inductors "6 I '62 have no substantial pf 0'. comp nent. The't'wo adjustable inductancs "68' are mounted in the same housing as "the rationi- "e'tr' to form a complete receiver unit "and are sorbet the receiver units are interchangeable I and ay be replaced without the" necessity of any fur- "ma adjustment.

y In operation, the raucmeter measures" theratio of the twdcurrents' through the inductors. The

"actual magnitudes of these' currents will depend on the'supply voltage and on' the impedanceof the inductors which impedance includes aieactance dependent on the frequency of the supply. Itwill readily'be seen that the ratio of the currents is independent-of variations in the supply voltage. In order that the ratio of the currents should "be independent of frequency it is necessary with the apparatus described to make the power factor of the inductors very small and low less coils are-thereforeemployed. Preferably the power factor is made less tha'n'0.2.

The particular details or construction and-ad- Jus'tment of the receivers form no part of the pres- 1 cut invention and in describing the setting up'of similarly positioned with regard to their respective coils. Then by means of the four holes 31, the sleeve I1 is rotated to adjust the spring tension until the correct reading, i. e. mid-point of scale is obtained. The spring adjuster is then locked by means of the locking tab 38 and the nut 39.

In this position rotation of the stator relative to the armature will have no effect since the armatures are similarly situated with regard to their respective coils. Then the pressure is removed from the bellows. When the armature is not in its midway position (i. e. not symmetrically situated with regard to the coils) the relative inductances will be changed by rotation of the stator. The stator is rotated until a zero pressure reading is obtained and then locked by means of the four nuts 41 which are provided with locking tab washers 53. Then the nut 39 is slackened so that the grub-screw 40 can be adjusted to limit the armature travel at the desired overload pressure, after which the nut 39 is again tightened.

It will be particularly noted that by providing these facilities for adjustment of the transmitters and receivers, all the transmitters and all the reeeivere can be'm'ade interchangeablewithoutthe necess ty for'rresh adjustment cninstauaucrram "replacement despite the differences that' ari'sein the normal course of manufacture 'between 'dlfferen't I instruments.

We claim: I d I 1. An electrical indicating device comprising-a "pair or inductors spaced apart *an'd energized in parallel by arr alternating current power"*supply, an armature *disposedbeside' the 'inductorsjsai'd armature being linearly movable relative to the inductors so that the ratio of the impedancesof the inductors variesaccordingto the lineardisplacement andlieing rotatable relative to the inductors about an axis lyin'g' -in the" direction" or linear movement, said armature-being shaped-so thatrotation' relative-to the inductors simultaneously moves the armature towards cr away rrcm both inductors.

An electrical indicating device'comprlsing a pair of inductors spaced apart a'nd energized in parallel by an alternating current power supply, an armature mounting disposed-beside the indu'ctors, which mounting is linearly movabler'elative to the inductorsand rotatable 'relative to the inductors about an axislyin'g 'inthe direction 6f tl'ielinear-movement, a pair of armatures'carried on said mounting and associated respectively-with imultaneously moves '3. An electricalindicati'ng devicecompris'ingan armature mounting, two armatures spaced apart om said mounting, a-p'air'of inductorsassociated respectively with the two'-armaturesandenergized in parallel by an alternating 'current poWershpply, each inductor being formedby two-coils connected in series and disposed at equal distances on opposite sides of the armature mounting, which mounting is linearly movable relative to the inductors and rotatable relative to the inductors about an axis lying in the direction of the linear movement, the two armatures being spaced apart on the mounting in the direction of linear movement a distance difiering from the spacing of the inductors so that the ratio of the impedances of the inductors varies in accordance with the displacement of the mounting and the armatures being shaped so that rotation of the mounting relative to the inductors simultaneously moves both armatures towards or away from the coils of their respective inductors.

4. An electrical indicating device comprising an armature mounting, two armatures spaced apart on said mounting, a pair of inductors associated respectively with the two armatures and energised in parallel by an alternating current power supply, each inductor being formed by two coils connected in series and disposed at equal distances on opposite sides of the armature mounting, which mounting is linearly movable relative to the inductors and rotatable relative to the inductors about an axis lying in the direction of the linear movement, the two armatures being spaced apart on the mounting in the direction of linear movement a distance differing from the spacing of the inductors, the armatures being non-circular in shape in a plane at right angles to said direction of linear movement and having a diameter in one direction in said plane greater than the diameter in a transverse direction.

5. An electrical indicating device according to claim 4 wherein the two coils of each inductor are co-axial, the axis of the two inductors being at right angles to one another and to said direction of linear movement and wherein the two armatures are of similar shape but with their corresponding diameters at right angles to one another.

6. An electrical indicating device comprising a housing, an armature mounting linearly movable in the housing, a coil support rotatably mounted in the housing for rotation about an axis lying in the direction of the linear movement of the armature mounting, a pair of inductors mounted on said coil support and spaced apart in said direction of linear movement, a pair of armatures carried on said armature mounting associated respectively with the two inductors, the armatures being spaced apart a distance differing from the spacing of inductors and shaped so that rotation of the coil support in the housing simultaneously moves both inductors towards or away from their respective armatures.

7. An electrical indicating device comprising a pair of inductors spaced apart and energised in parallel by an alternating current power supply, an armature mounting disposed beside the inructors, which mounting is linearly movable relative to the inductors and rotatable relative to the inductors about an axis lying in the direction of linear movement, and a pair of armatures carried on said mounting and associated respectively with the two inductors which armatures are spaced apart on the mounting in the direction of linear movement a distance greater than the spacing of the inductors so that the ratio of the impedances of the inductors varies in accordance with the displacement of the mounting, the armatures having a diameter in one direction, at

right angles to the direction of linear movement, which is greater than a diameter in a different direction at right angles to the direction of linear movement, rotation of the said mounting relative to the inductors simultaneously moving both armatures towards or away from their respective inductors.

8. A pressure indicator comprising a pair of inductors spaced apart and energised in parallel by an alternating current power supply, an armature mounting disposed beside the inductors which mounting is linearly movable relative to the inductors and rotatable relative to the inductors about an axis lying in the direction of the linear movement, a pair of armatures carried on said mounting and beside said inductors, said armatures being spaced part on the mounting in the direction of linear movement a distance differing from the spacing of the inductors so that the ratio of the impedances of the inductors varies in accordance with the displacement of the mounting, the armatures each having a substantially circular periphery and having segments cut away from predetermined portions of said peripheries, rotation of the said mounting relative to the inductors simultaneously moving both armatures towards or away from their respective inductors.

ERIC BEECROFT MOSS. CHARLES WILLIAM COOPERh' REFERENCES CITED The following references are of record in th file of this patent:

UNITED STATES PATENTS Number Name Date 2,183,078 Kemler Dec. 12, 1939 2,390,328 Roberts Dec. 4, 1945 2,390,463 Roters Dec. 4, 1945 2,408,524 Mestas Oct. 1, 1946 2,417,097 Warshaw Mar. 11, 1947 2,430,757 Conrad Nov. 11, 1947 

